Magneto-optical method and apparatus for determining properties of reservoir fluids

Abstract

A method for determining a property of earth formations surrounding a borehole includes the following steps: deriving a fluid sample downhole in the borehole, subjecting the sample while downhole to a magnetic field; measuring a magneto-optical shift of a beam of electromagnetic radiation passed through the sample, and determining the property from the measured magneto-optical shift.

1. Apparatus for determining a property of earth formations surrounding a borehole, comprising:
 a device deployed in the borehole for obtaining a sample of fluid; 
 a magnet in said device for subjecting said sample to a magnetic field; 
 a source of polarized electromagnetic radiation in said device for passing a beam of polarized electromagnetic radiation through said sample; and 
 a detector for detecting the magneto-optical shift of said beam of polarized electromagnetic radiation passed through the sample. 
 
   
   
     2. Apparatus as defined by  claim 1 , wherein said property is the dielectric permittivity of the fluid of said earth formations. 
   
   
     3. Apparatus as defined by  claim 1 , wherein said property is the Verdet constant of the fluid of said earth formations. 
   
   
     4. Apparatus as defined by  claim 1 , wherein said property is a molecular property of the fluid of said earth formations. 
   
   
     5. A method for determining a property of earth formations surrounding a borehole, comprising the steps of:
 deriving a fluid sample downhole in the borehole; 
 subjecting the sample while downhole to a magnetic field; 
 measuring a magneto-optical shift of a beam of electromagnetic radiation passed through said sample; and 
 determining said property from said measured magneto-optical shift. 
 
   
   
     6. The method as defined by  claim 5 , wherein said property is the dielectric permittivity of the fluid. 
   
   
     7. The method as defined by  claim 6 , further comprising determining asphaltene concentration from said dielectric permittivity of the fluid. 
   
   
     8. The method as defined by  claim 6 , further comprising determining water cut in the fluid from said dielectric permittivity of the fluid. 
   
   
     9. The method as defined by  claim 6 , further comprising determining the extent of contamination of the fluid by drilling fluid from said dielectric permittivity of the fluid. 
   
   
     10. The method as defined by  claim 6 , further comprising determining the fluid types and fractional volumes of the fluid from said dielectric permittivity of the fluid. 
   
   
     11. The method as defined by  claim 6 , wherein said steps of subjecting the sample to a magnetic field and determining the magneto-optical shift of a beam of electromagnetic radiation passed through the sample include subjecting the sample to a static magnetic field; passing polarized light through said sample; and determining the polarization shift of the light that has passed through the sample. 
   
   
     12. The method as defined by  claim 5 , wherein said property is the Verdet constant of the fluid. 
   
   
     13. The method as defined by  claim 5 , wherein said property is a molecular property of the fluid. 
   
   
     14. The method as defined by  claim 5 , wherein said steps of subjecting the sample to a magnetic field and determining the magneto-optical shift of a beam of electromagnetic radiation passed through the sample include subjecting the sample to a static magnetic field; passing polarized light through said sample; and determining the polarization shift of the light that has passed through the sample. 
   
   
     15. The method as defined by  claim 14 , wherein said steps of passing polarized light through said sample and determining the polarization shift of the light that has passed through the sample comprises:
 providing an input light having an input plane of polarization; 
 passing the input light through the sample; 
 measuring an output plane of polarization of output light exiting the sample; and 
 determining the polarization shift as a function of the input plane of polarization and the output plane of polarization. 
 
   
   
     16. The method as defined by  claim 15 , wherein said step of determining the polarization shift as a function of the input plane of polarization and the output plane of polarization comprises determining said polarization shift as a function of the difference between the output plane of polarization and the input plane of polarization. 
   
   
     17. The method as defined by  claim 14 , wherein said step of deriving a sample of fluid comprises: providing a logging device in the borehole; causing the fluid to pass into a flow line of the logging device; and providing a cell in the flow line that receives the fluid, said cell having a substantially transparent region through which said electromagnetic radiation is passed. 
   
   
     18. The method as defined by  claim 17 , wherein said step of subjecting the sample to a magnetic field comprises providing a magnet in said logging device, and wherein said steps of passing polarized light through the sample and determining the polarization shift of the light that has passed through the sample are performed in said logging device. 
   
   
     19. The method as defined by  claim 5 , wherein said step of deriving a sample of fluid comprises: providing a logging device in the borehole; causing the fluid to pass into a flow line of the logging device; and providing a cell in the flow line that receives the fluid, said cell having a substantially transparent region through which said electromagnetic radiation is passed. 
   
   
     20. The method as defined by  claim 19 , wherein said cell is transmissive of said electromagnetic radiation. 
   
   
     21. The method as defined by  claim 19 , wherein said cell is reflective of said electromagnetic radiation. 
   
   
     22. The method as defined by  claim 5 , wherein said sample comprises fluid obtained from one or more of the formations. 
   
   
     23. The method as defined by  claim 5 , wherein said sample comprises fluid obtained from drilling fluid in the borehole. 
   
   
     24. The method as defined by  claim 5 , wherein said method is performed by a device suspended in said borehole on a wireline. 
   
   
     25. The method as defined by  claim 5 , wherein said method is implemented by a tool on a drill string. 
   
   
     26. The method as defined by  claim 5 , wherein at least a part of said step of determining said property from said measured magneto-optical shift is performed downhole. 
   
   
     27. The method as defined by  claim 5 , wherein at least a part of said step of determining said property from said measured magneto-optical shift is performed uphole. 
   
   
     28. The method as defined by  claim 5 , wherein said steps of subjecting the sample to a magnetic field and measuring a magneto-optical shift of a beam of electromagnetic passed through the sample is performed while said sample is substantially stationary. 
   
   
     29. The method as defined by  claim 5 , wherein said steps of subjecting the sample to a magnetic field and measuring a magneto-optical shift of a beam of electromagnetic radiation passed through the sample is performed while said sample is in motion. 
   
   
     30. The method as defined by  claim 5 , wherein said steps of subjecting the sample to a magnetic field and measuring a magneto-optical shift of a beam of electromagnetic radiation passed through the sample is performed while said sample is flowing in a flow line. 
   
   
     31. A method for determining a property of earth formations surrounding a borehole, comprising the steps of:
 deriving a database that relates a number of known parameters of test fluid samples to test measurements of the magneto-optical shift of light passed through the test samples; 
 deriving a fluid sample downhole in the borehole; 
 subjecting the sample while downhole to a magnetic field and measuring a magneto-optical shift of a beam of electromagnetic radiation passed through said sample; and 
 determining said property of the earth formations by using said measured magneto-optical shift and said database. 
 
   
   
     32. The method as defined by  claim 31 , wherein said property corresponds to one of the known parameters of the test fluid samples. 
   
   
     33. The method as defined by  claim 32 , wherein said known parameters of the test fluid comprise dielectric permittivity, temperature, and pressure. 
   
   
     34. The method as defined by  claim 31 , wherein said property is the dielectric permittivity of the fluid. 
   
   
     35. The method as defined by  claim 31 , wherein said property is the Verdet constant of the fluid.